`extends ArrayBufferLike` works for own package; but causes errors for downstream users

TypeScript Version: 3.5.1

Search Terms:

• extends ArrayBufferLike
• TS2312
• An interface can only extend an object type or intersection of object types with statically known members.

Code

Repro,
https://github.com/AnyhowStep/ts-issue-35172

The line of code that introduced the problem,
https://github.com/AnyhowStep/type-mapping/commit/cb420b8e14dda4de5bf017bcc4a3ab3f35e71de5#diff-f84343d86daf9a112cfa32bdb89c7cdaR2

The following is safe to use on own package and downstream packages,

interface Buffer {
    ___doesNotExist? : any;
}

The following causes downstream packages to break,

interface Buffer extends ArrayBufferLike {
    ___doesNotExist? : any;
}

Expected behavior:

Option A:

• Should crash for own package
• Should crash for downstream packages

Option B:

• Should not crash for own package
• Should not crash for downstream packages

Actual behavior:

• Does not crash for own package
• Crashes for downstream packages

Playground Link:

None.

But I have repro steps,

https://github.com/AnyhowStep/ts-issue-35172

Related Issues:

None that I could find.

リンクされている AnyhowStep/ts-issue-35172 の再現から始め、issue 内の 2 つの Buffer 宣言を、参照されている type-mapping commit も含めて比較してください。downstream-package の失敗を確認し、compiler がその宣言を一貫して拒否すべきか、一貫して受け入れるべきかを判断してください。選択した挙動を再現し、適切な regression test でカバーできれば完了です。